Common Chimney problems: Blocked Flues, Creosote & Birds Nests
Understanding Creosote Build-Up and How to Remedy It
Heavy Creosote build up
This video shows the creosote build-up inside a customer's chimney, caused by slumbering their stove overnight. The creosote in this case is particularly runny, which occurs when wood is burned at low temperatures, producing more moisture in the smoke. This moisture causes the creosote to remain in a liquid form, making it more likely to coat the chimney walls and increase the risk of a chimney fire if not properly cleaned.
What can remedy this problem:
Regular chimney sweeping is essential to remove hazardous creosote build-up and restore proper airflow. To avoid excessive creosote formation, it’s important to burn dry, seasoned wood at higher temperatures, rather than slumbering the stove overnight. For a period, burning smokeless coal, which burns hotter, can help dry out the creosote, making it easier to remove during the sweep. If there’s significant creosote, we can use chemical powders added to the fire, which assist in drying out the creosote. However, these powders are not a complete solution and should be followed by a professional chimney sweep to ensure thorough cleaning. Our expert service ensures that your chimney stays safe and efficient, while minimizing the risk of chimney fires.
A Serious Chimney Hazard
I recently visited a customer who had just moved into their new home and wanted to check the stove and chimney before using it. It’s a good job they did because the situation was far from safe.
Crystallised Creosote
After sweeping the chimney, I noticed a concerning problem—the rods didn’t move freely, and a significant amount of hardened deposits came down. These weren’t just soot; they were signs of stage 2 creosote, a dangerous substance that forms from inefficient wood burning and poor chimney maintenance.
To investigate further, I sent a camera up the flue. What I found confirmed the worst: a massive build-up of crystallised creosote had corroded the liner so badly that it had a hole. This made the chimney completely unsafe to use.
I really felt for the new owners, as this was a problem they’d inherited without knowing.
If you're moving into a new home, or haven’t had your chimney checked in years, it’s vital to get it inspected and swept. Issues like this don’t just happen overnight—they build up over time and can pose serious risks to safety.
birds nest in a chimney
Blockage Caused by a Birds Nest
Here’s the bottom of a bird’s nest I discovered in a chimney recently. This is a common problem in chimneys that have no cowl on the pot. In this case, the chimney had a gas fire installed, but the lack of a cowl left it open, creating an opportunity for birds to nest inside.
Crows are notorious for building nests in chimneys, often causing blocked flues, which can pose serious risks to your home and health. Their nesting process is surprisingly methodical—they drop twigs and sticks down the chimney one by one. When a stick wedges against the sides of the flue, they continue until a sturdy structure forms. Once the base is solid, they line the nest to create a safe spot for their young
In this case, the nest was just a few metres from the bottom, completely blocking the flue. Blockages like this are incredibly dangerous, especially with gas fires, as they can stop toxic gases like carbon monoxide from escaping properly.
If your chimney doesn’t have a cowl fitted, it’s at risk of becoming a nesting spot. Regular chimney sweeps and a properly fitted cowl can prevent this and keep your home safe. Additionally, it’s essential to have a carbon monoxide alarm fitted in any room with a gas fire, stove, or open fire. These alarms provide an extra layer of protection by detecting dangerous gases that could leak into your home due to blockages or other issues.
